Device for Clamping a Tool Insert in a Grinding Machine

ABSTRACT

The insert ( 2 ) is placed on the reception surface ( 10 ) of the interchangeable support ( 9 ). A simple movement of the piston ( 35 ) towards the right in the barrel ( 7 ) of the headstock ( 1 ) drives the cam ( 32 ) so that the lever ( 13 ) pivots and moves, introducing its nose ( 15 ) into the bore ( 27 ) of the insert, the nose drawing the insert rearwards, which is then pressed against the vertical face ( 11 ) of the support, the insert also being pressed against the horizontal face ( 10 ) of the support under the effect of the locking shoe ( 13 ), which makes it possible to fix the insert in an exactly determined position. The measuring device ( 12 ) determines this position by means of a position sensor ( 20 ) and controls the grinding operations.

The object of the present invention is a device for clamping a tool insert in a grinding machine, in particular for sharpening it.

It is known that machining centres performing turning, milling, drilling, boring or other operations use amongst other things tools composed of a high-strength steel body to which there is fixed a tip or insert that has one or more cutting edges. These inserts, made from materials of very high hardness and strength, such as tungsten carbide (TC) or titanium carbide, cermets, etc must have cutting edges cut with precision and sharpened within tight tolerances by grinding and finishing so that their use on numeric control machining centres guarantees the result of the programmed machinings.

In order to obtain the required precision, it is necessary, during the grinding and sharpening operation, for the insert to be positioned very precisely and held firmly. To this end, the inserts have, from manufacture, a bore that passes right through them and forms a dimensional reference, supplemented by a heel face opposite to the cutting edge.

The aim of the present invention is to create a clamping device that positions and fixes an insert in a reliable and rigorous manner with respect to a system of axes related to the grinding machine, so that the grinding and sharpening operations on the cutting edge or edges can be directed by numeric control and therefore be performed at very high speed. In addition the invention aims to permit automated positioning and removal of inserts that are as easy as possible.

To this end, the present invention concerns a device for clamping a tool insert in a grinding machine, in particular for sharpening it, characterised by a body intended to be mounted on a headstock of the machine and provided with an interchangeable support that has reception surfaces for the insert, and by a clamping lever pivoting in a slot in the body, the said clamping lever being provided with a locking nose and a support shoe, these elements being brought into abutment on the insert by moving the clamping lever under the effect of the movement of a piston housed in the headstock and controlling the lever by means of a cam.

The interchangeable support may be an attached piece, fixed to the body and sized so that the reception surfaces position the insert precisely with respect to the axis of the piston.

The locking nose of the clamping lever may be conformed so as to engage in a bored hole in the insert and act on the flank of this hole.

The interchangeable support may have two reception surfaces for the insert, oriented perpendicular to each other, one of them being perpendicular to the axis of the piston.

The support shoe may be an independent piece mounted on the clamping lever by means of a pin allowing a pivoting of the shoe which brings one edge of the latter into abutment against a support surface of the lever when a stop surface of the shoe abuts against a support surface of the insert.

The pivoting of the clamping lever in a slot in the body may be effected by a cylindrical pin engaged in an oblong hole in the cheeks of the body, so as to allow a combined rotation and translation movement of the clamping lever with respect to the body.

The cam may be fixed at the end of the piston of the headstock and comprise a profile with a notch extended on each side by a ramp, these profile elements cooperating with a rear head of the lever.

A measuring device comprising a position sensor may be associated with the body of the device, so as to engage in a bore of the insert held clamped by the lever, in order to detect its exact position and control the grinding operations, the cutting edge or edges of the inserts being located with respect to the said bore.

A description is given below, by way of example, of an embodiment of the object of the invention, depicted in the accompanying drawings, where

FIG. 1 is a view, in lateral perspective and plan view, of the clamping device,

FIG. 2 is a view in section of this device along a vertical plane passing through the axis of the headstock, to an enlarged scale, and

FIG. 3 is a view in section similar to that in FIG. 2, showing the device in the clamped position on an insert.

As depicted in the drawings, the device is mounted on a work-holder headstock 1 of a grinding machine whose tools are controlled so as to be able to attack the parts to be ground on an insert blank 2, for example in the form of a semicircular disc.

The main part of the device is a body 3 having the general shape of a rectangular parallelepiped with one end with pyramidal faces 4 at its front end. This piece has, throughout its length, a slot 5 along a vertical plane in its axis of symmetry, opening out in a bore 6 which allows the engagement of the cylindrical barrel 7 of the headstock 1. The body 3 is fixed to the barrel 7 by screws 8 engaged in corresponding holes that pass through the two cheeks of the body 3 separated by the slot 5.

An interchangeable support 9 adapted to the dimensions of the inserts 2 to be machined is fixed under the body 3. This piece has two insert reception faces 10 and 11, the exact arrangement of which will be explained below, and is arranged to cooperate with a position sensor 20 actuated by a measuring device 12, for example of the Renishaw type, in order to locate the exact position of the insert clamped in the device and to control the grinding.

When an insert 2 has been placed on the reception surface 10 of the support 9, its clamping is effected by means of a clamping lever 13, which is provided with a U-shaped support shoe 14 and whose cheeks are engaged on each side of the front part of the lever 13, in the form of a nose 15.

FIGS. 2 and 3 show the arrangement of the interchangeable support 9 and the control of the clamping lever 13. In fact the device will comprise a set of interchangeable supports 9 adjusted to the dimensions of various inserts. This is because the inserts to be machined, sharpened or cut, can be of variable dimensions, for example with a diameter from 6 to 32 mm and a thickness from 2 to 8 mm. Whereas, so that the machinings take place evenly, it is necessary for the mid-plane of the insert to be positioned in line with the axis of the headstock 1. It is therefore necessary for the interchangeable supports 9 to constitute a precise positioning device. For this purpose, they can for example have a heel 16 and a support face 17 which correspond to the opposing faces of the body 3 and are disposed according to a given insert model. A screw 18 engaged in a bore in the support 9 and in a thread in the body 3 fixes the support so that the faces 16 and 17 are pressed against the reception surfaces of the body 3. For this purpose, the axis of the bore and of the thread receiving the screw 18 is slightly oblique with respect to the heel 16, itself perpendicular to the support face 17. Each interchangeable support has a bore 19 for engaging the position sensor 12, this bore opening out in the support face 10 which, with the heel face 11 perpendicular to the axis of the headstock, specifies the positioning of the insert. The bore 19 is situated in line with a bore 27 of the insert, which represents its positioning reference. The two surfaces 10 and 11 are adjusted according to the dimensions of the insert, the heel being perpendicular to the axis of the headstock 3 and the face 10 perpendicular to the plane of symmetry of the device, and therefore parallel to the axis of the headstock.

The mounting and control of the clamping lever 13 result from FIGS. 2 and 3. This lever is engaged and guided in the slot 5, and its axis 22 housed in oblong holes 23 in the cheeks of the body 3. At its front end the lever has a nose 15 conformed so as to be able to engage halfway into the bore 23 of the insert blank 2. In addition the support shoe 14, in the form of a U and held on the lever 13 by a pin 24, is arranged with a pressing face 25 and a support face 26 which, in the active position (FIG. 3), transmit a sufficient clamping force to the insert to fix it and allow the grinding operations. It should be noted that the geometry of these elements is arranged so that the pin 24 in principle undergoes no stress.

At its rear end the lever 13 has a head 28 which cooperates with a given profile of a cam 32 engaged in the slot 5 in the body 3. This profile comprises two ramps 30 and 31 and between them a notch 29 adjusted to the head 28 of the lever 13. The cam 32 is fixed by a screw 33 in a vertical diametral slot in an end piece 34 fixed to the end of the piston 35 of a cylinder acting inside the barrel 7 of the headstock 1.

It will be understood that FIG. 2 illustrates the release position. The piston 35 is in the advanced position. The cam 32, by means of the ramp 30, holds the lever 13 in a position in which the nose 15 is released from the support 9. An insert 2 can be placed on the support or raised from the latter.

On the other hand FIG. 3 illustrates the position reached when the piston 35 has been withdrawn. The end piece 34 has moved the can 32 parallel to itself so that the head 28 of the lever 13 has been raised by the ramp 31. The nose 15 has engaged in the bore 27, pressing the insert 2 against the heel 11 whilst the shoe 14, pressed by the face 25 of the lever and bearing through its face 26, on the insert, presses the latter firmly on the face 10 of the interchangeable support. The oblong holes 23 allow a combined translation and pivoting movement of the lever 13. In addition the slope of the ramp 31 of the cam provides multiplication of the vertical force exerted by the shoe 14 with respect to the movement force of the piston 35. It is possible to obtain degrees of multiplication of the forces of 2 to 5, so that the scope of use of the device is extremely wide.

Thus a simple and single movement of the piston 35 makes it possible to obtain a combined action with three effects:

introduction of the nose 15 of the clamping lever in the bore 27 of the insert,

possible movement of the insert towards the rear under the effect of the nose 15 and abutment of the insert against the heel face 18 of the interchangeable support,

effect of pressing the insert against the face 10 of the interchangeable support by means of the shoe 14. 

1-8. (canceled)
 9. A device for clamping a tool insert in a grinding machine, in particular for sharpening it, comprising a body intended to be mounted on a headstock of the machine and provided with an interchangeable support which has reception surfaces for the insert, and a clamping lever pivoting in a slot in the body, the said clamping lever being provided with a locking nose and a support shoe, these elements being brought into abutment on the insert by moving the clamping lever under the effect of the movement of a piston housed in the headstock and controlling the lever by means of a cam.
 10. Device according to claim 9, wherein the interchangeable support is an attached piece, fixed to the body and sized so that the reception surfaces position the insert precisely with respect to the axis of the piston.
 11. Device according to claim 9, wherein the locking nose of the clamping lever is conformed so as to engage in a bored hole in the insert and act on the flank of this hole.
 12. Device according to claim 11, wherein the interchangeable support has two reception surfaces for the insert, oriented perpendicular to each other, one of them being perpendicular to the axis of the piston.
 13. Device according to claim 11, wherein the support shoe is an independent piece mounted on the clamping lever by means of a pin allowing a pivoting of the shoe which brings one edge of the latter into abutment against a support surface of the lever when a stop surface of the shoe abuts against a support surface of the insert.
 14. Device according to claim 11, wherein the pivoting of the clamping lever in a slot in the body is effected by a cylindrical pin engaged in an oblong hole in the cheeks of the body, so as to allow a combined rotation and translation movement of the clamping lever with respect to the body.
 15. Device according to claim 9, wherein the said cam is fixed at the end of the piston of the headstock and comprises a profile with a notch extended on each side by a ramp, these profile elements cooperating with a rear head of the lever.
 16. Device according to claim 9, wherein a measuring device comprising a position sensor is associated with the body of the device, so as to engage in a bore of the insert held clamped by the lever, in order to detect its exact position and control the grinding operations, the cutting edge or edges of the inserts being located with respect to the said bore. 